1. Field of the Invention
The invention concerns a method for desalting water by reverse osmosis, as well as a device for the implementation of that method.
2. Description of the Related Art
A method and device for desalting water are known from WO 97/21483. Here, the salt water is pressurized by applying an exterior pressure to a pressure medium, the pressure of which is then transferred to the salt water. The design of one embodiment is such, that the salt water at first is pumped by a first pump into a first chamber of a three-chamber configuration at relatively low pressure. Subsequently, a high-pressure pump applies a high pressure to a pressure medium in a second chamber of the three-chamber configuration, which results in the saltwater in the first chamber to be conveyed into the membrane module at the high pressure necessary for reverse osmosis. Simultaneously, the concentrated salt water, which has not penetrated through the membrane of the membrane module, is conveyed into a third chamber of the three-chamber configuration. Finally, the next delivery of salt water by the first pump into the first chamber results in the concentrated salt water being discharged from the third chamber, and ultimately from the device.
In this known method the high-pressure pump delivers a pressure medium at a high pressure level to the membrane modules, and no longer has to pump salt water, as has been the case in other known methods, and which due to the salt water's oxidation potential exacted high demands on the material of the pump, which significantly increased its costs. But a high-pressure pump to create the pressure necessary for reverse osmosis is still required, which has a negative effect on the energy balance, and consequently on the overall efficiency of the device. In addition, the known method operates in two processing steps, whereby one of the two processing steps generates desalted water, while the other processing step re-supplies salt water and discharges the concentrated salt water.